We've all been there. Your monkey is throwing a fit, jumping on the furniture, screeching like a furry banshee and hurling unmentionable things all over the place. At times like this, wouldn't it be great if you could just shine a light and control the monkey’s brain? Sorry, that isn’t possible (yet), but researchers have succeeded in stimulating a monkey’s brain with a remarkable level of precision using impulses of light aimed at specific kinds of neural cells. It may not be much help to desperate monkey owners, but it does provide hope of new treatments for sufferers of many neurological disorders.